CN1131086A - Branched polycarbonate preforms, blow moldable polycarbonates, and method for making - Google Patents

Abstract

Blow moldable polycarbonate is produced by first producing a polycarbonate preform by a melt transesterification process. The polycarbonate preform comprises 2.1 to 10 mole percent polyfunctional branching agent, based on the total moles of polycarbonate in the polycarbonate preform. The polycarbonate preform is then melt equilibrated with a second polycarbonate to produce a blow moldable grade.

Description

Branched polycarbonate preform, blow-moldable polycarbonate and preparation method thereof

This application is a continuation-in-part of US Application Serial No. 08/325,769.

The invention relates to a branched polycarbonate composition and a preparation method thereof. More specifically, the present invention relates to polycarbonate preforms comprising branching agents and methods of making them by melt transesterification. The present invention also relates to a process for preparing a blow moldable polycarbonate by melt equilibrating a mixture comprising a second polycarbonate for a polycarbonate preform. It also relates to blow-moldable polycarbonates produced by this method.

Polycarbonate is a well-known high-performance engineering thermoplastic characterized by a number of excellent physical properties, including optical clarity, toughness, dimensional stability and excellent impact strength over a wide temperature range. To make it suitable for blow molding applications, polycarbonate resins must also exhibit sufficient melt strength and viscosity.

In blow molding, a tube of molten plastic is extruded through a die suspended above the mold. The tube, or parison, is then sandwiched between the two mold halves. Air is injected into the parison to inflate the plastic, forcing it against the walls of the mold to form the desired shape. For a resin to be blown, it must have sufficient melt strength and viscosity to hang from the die until it is sandwiched between the mold halves. It has been found that polycarbonates with polyfunctional branching agents such as 1,1,1-tris(4-hydroxyphenyl)ethane condensed on the polymer backbone provide the necessary melt strength and viscosity.

In the prior art, the polycarbonate is first obtained by interfacial polymerization, and then a multifunctional branching agent is mixed into it. Such a process is disclosed in US Patent 5,097,008 to Krabbenhoft et al., wherein an unbranched cyclic aromatic polycarbonate is contacted with a polyfunctional branching agent under melt polymerization conditions. Similarly, in US Patent 4,888,400, Krabbenhoft et al. contacted an unbranched linear aromatic polycarbonate with a polyfunctional branching agent under melt polymerization conditions. Polycarbonates useful for blow molding applications can be prepared by the methods described in these two patents. However, in the methods used in this prior art, the concentration of branching agent that can be introduced into the polymer is generally below 2.0 mole % in order to minimize the possibility of gelation.

It is desirable to be able to produce preforms which may contain high concentrations, preferably greater than 2.0 mole percent, of branching agents. Such preforms are then melt equilibrated with any grade of polycarbonate to produce blow moldable grade preforms.

The prior art requires batch production of branched polycarbonates suitable for blow molding in a one-step operation. This requires the manufacturing facility to stop production and switch to producing blow-moldable grade preforms. After a batch of blow-moldable grade material has been manufactured, production must then be stopped again to switch back to standard grade preforms.

Manufacturers would like to be able to produce standard grades of polycarbonate preferably without interruption. This standard grade can then be melt equilibrated with a preform in a separate operation to produce blow moldable polycarbonate. This allows for the production of blow-moldable polycarbonate without interrupting the manufacturing process.

Multifunctional branching agents can be conveniently incorporated by coextrusion with polycarbonate. However, the incorporation of polyfunctional branching agent monomers into polycarbonate resins can be accomplished by reducing the molecular weight relative to that of the base resin. This decrease in resin molecular weight is observed for any hydroxyl-containing additive under conditions where the additive can react with the polycarbonate backbone. Branched polycarbonates prepared according to the Krabbenhoft process can also exhibit a decrease in molecular weight and viscosity after branching relative to unbranched starting materials. It would therefore also be desirable to be able to provide a method for incorporating branching agents into polycarbonates without significantly reducing the molecular weight or viscosity relative to the molecular weight or viscosity of the unbranched polycarbonate resin.

The invention provides a kind of method for preparing blow molding polycarbonate, it comprises the steps:

a. making a branched polycarbonate preform by contacting a polyfunctional branching agent, a diaryl carbonate, and a dihydric phenol in a melt transesterification process; and

b. Melt equilibrating the polycarbonate preform with a second polycarbonate.

The present invention also provides a method of preparing a polycarbonate preform comprising the step of contacting a polyfunctional branching agent, a diaryl carbonate and a dihydric phenol in a melt transesterification process wherein the concentration of the polyfunctional branching agent is , based on the total moles of structural carbonate units of the polycarbonate preform, it is 2.1-10% (mole).

The present invention also provides polycarbonate preforms comprising from 2.1 to 10 mole percent of a polyfunctional branching agent, wherein the mole percents are based on the total moles of structural carbonate units of the polycarbonate preform.

The method for producing blow-moldable polycarbonate provided by the present invention is: at first produce the polycarbonate preform that comprises more than 2 (mole) branching agent by melting transesterification method, then this preform and the second polycarbonate Esters Melt Equilibrium. The present invention also provides polycarbonate preforms and blow moldable polycarbonates.

The polycarbonate preform is prepared by synthesizing polycarbonate while mixing a branching agent. This can be achieved by melt polymerizing diaryl carbonate, dihydric phenol and polyfunctional branching agent. The polymerization reaction can be carried out at a temperature of 170-380°C in the presence of an effective amount of a polymerization catalyst such as tetramethylammonium acetate or tetramethylammonium formate. Those skilled in the art can determine the necessary amount of polymerization catalyst to use. Typical amounts of catalyst used are from 0.5 x 10 ^-6 to 5 x 10 ^{-2 wt} %, based on the weight of reagents in the melt polymerization mixture.

Other polymerization catalysts include tetramethylammonium acetate, aryl ammonium and aryl phosphonium hydroxides, carboxylates, phenates and borates.

Diaryl carbonates useful in the production of polycarbonate preforms include, but are not limited to, diphenyl carbonate; bis(halophenyl)carbonates such as bis(chlorophenyl)carbonate and bis(bromophenyl)carbonate ; bis(alkylbenzene) carbonates such as bis(toluene) carbonate, bis(ethylbenzene) carbonate and bis(cumyl)carbonate; bis(nitrophenyl)carbonate; and mixtures thereof. Diphenyl carbonate is preferred.

Examples of dihydric phenols useful in the practice of the present invention for preparing polycarbonate preforms include the following compounds:

Resorcinol

4-Bromoresorcinol

Hydroquinone

4,4′-Dihydroxybiphenyl

1,6-Dihydroxynaphthalene

2,6-Dihydroxynaphthalene

Bis(4-hydroxyphenyl)methane

Bis(4-hydroxyphenyl)diphenylmethane

Bis(4-hydroxyphenyl)-1-naphthylmethane

1,1-bis(4-hydroxyphenyl)ethane

1,2-bis(4-hydroxyphenyl)ethane

1,1-bis(4-hydroxyphenyl)-1-phenylethane

2,2-Bis(4-hydroxyphenyl)propane (“Bisphenol A”)

2-(4-Hydroxyphenyl)-2-(3-hydroxyphenyl)propane

2,2-bis(4-hydroxyphenyl)butane

1,1-bis(4-hydroxyphenyl)isobutane

1,1-bis(4-hydroxyphenyl)cyclohexane

1,1-bis(4-hydroxyphenyl)cyclododecane

trans-2,3-bis(4-hydroxyphenyl)-2-butene

2,2-bis(4-hydroxyphenyl)adamantane

α,α'-bis(4-hydroxyphenyl)toluene

Bis(4-hydroxyphenyl)acetonitrile

2,2-bis(3-methyl-4-hydroxyphenyl)propane

2,2-bis(3-ethyl-4-hydroxyphenyl)propane

2,2-bis(3-n-propyl-4-hydroxyphenyl)propane

2,2-bis(3-isopropyl-4-hydroxyphenyl)propane

2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane

2,2-bis(3-tert-butyl-4-hydroxyphenyl)propane

2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane

2,2-bis(3-allyl-4-hydroxyphenyl)propane

2,2-bis(3-methoxy-4-hydroxyphenyl)propane

2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane

2,2-bis(2,3,5,6-tetramethyl-4-hydroxyphenyl)propane

2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane

2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane

2,2-bis(2,6-dibromo-3,5-dimethyl-4-hydroxyphenyl)propane

α,α-bis(4-hydroxyphenyl)toluene

α,α,α′,α′-Tetramethyl-α,α′-bis(4-hydroxyphenyl)-p-xylene

2,2-bis(4-hydroxyphenyl)hexafluoropropane

1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene

1,1-Dibromo-2,2-bis(4-hydroxyphenyl)ethylene

1,1-dichloro-2,2-bis(5-phenoxy-4-hydroxyphenyl)ethylene

4,4'-Dihydroxybenzophenone

3,3-bis(4-hydroxyphenyl)-2-butanone

1,6-bis(4-hydroxyphenyl)-1,6-hexanedione

Ethylene glycol bis(4-hydroxyphenyl) ether

Bis(4-hydroxyphenyl) ether

Bis(4-hydroxyphenyl)sulfide

Bis(4-hydroxyphenyl)sulfoxide

Bis(4-hydroxyphenyl)sulfone

Bis(3,5-dimethyl-4-hydroxyphenyl)sulfone

9,9-bis(4-hydroxyphenyl)fluorene

2,7-dihydroxypyrene

6,6'-Dihydroxy-3,3,3',3'-tetramethylspiro(di)indane ("spirobiindane bisphenol")

3,3-bis(4-hydroxyphenyl)(2-benzo[c]furanone)

2,6-Dihydroxydibenzo-p-dioxin (p-dioxin)

2,6-Dihydroxythianthrene

2,7-Dihydroxythioxanthene

2,7-dihydroxy-9,10-dimethylphenazine

3,6-Dihydroxydibenzofuran

3,6-Dihydroxydibenzothiophene

2,7-Dihydroxycarbazole

A preferred dihydric phenol for use in making polycarbonate preforms is 2,2-bis(4-hydroxyphenyl)propane, also known as bisphenol A.

Any thermally processable, stable tri- or tetra-substituted branching agent can be used as the polyfunctional branching agent of the present invention. Polyhydric phenols suitable for use as branching agents in the present invention include any trihydric or tetrahydric phenol, for example, 1,1,1-tris(4-hydroxyphenyl)ethane (or 4,4',4" - ethylenetriphenol or THPE); 1,3,5-tris(2-hydroxyethyl)cyanuric acid (or 1,3,5-tris(2-hydroxyethyl)-1,3,5-tris oxazine-2,4,6-(1H,3H,5H)-trione); 4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptane; 2,2-di [4,4'-(dihydroxyphenyl)cyclohexyl]propane; 1,3,5-trihydroxybenzene (phloroglucinol); 1,2,3-trihydroxybenzene (1,2,3-benzene triphenol); and 1,4-bis(4',4"-dihydroxy-triphenylmethyl)benzene. Examples of the above compounds and other multifunctional branching agents useful in the present invention and methods for their preparation can be found in, for example, US Patent Nos. 3,799,953 and Re. 27,682.

Other commercially available polyfunctional branching agents useful in the present invention include, for example: 2',3',4'-trihydroxyacetophenone; 2,3,4-trihydroxybenzoic acid; trihydroxybenzophenone ; 2,4,4'-trihydroxybenzophenone; 2',4',6'-trihydroxy-3-(4-hydroxyphenyl)phenyl ethyl ketone (phloretin); pentahydroxyflavone ; 3,4,5-trihydroxyphenylethylamine; 3,4,5-trihydroxyphenylethanol; 2,4,5-trihydroxypyrimidine (isobarbituric acid); hydrated tetrahydroxy-1,4 - Benzoquinones; 2,2',4,4'-tetrahydroxybenzophenone and 1,2,5,8-tetrahydroxyanthraquinone.

Mixtures of two or more of the above polyfunctional branching agents may be used to impart particularly desirable properties to the branched polycarbonates.

While those skilled in the art will know of other multifunctional branching agents suitable for the practice of this invention, 1,1,1-tris(4-hydroxyphenyl)ethane (also referred to herein as THPE) is preferred because it can Get it at a cheaper price.

Based on the total moles of structural carbonate in the polycarbonate preform, the multifunctional branching agent can be added in an amount up to 10 mole percent; the concentration of the multifunctional branching agent is preferably 4-6 mole percent.

To make a blow moldable polycarbonate, the polycarbonate preform can be melt equilibrated with a second polycarbonate. The amount of polycarbonate preform added to the second polycarbonate should be sufficient to produce the desired branching agent concentration in the resulting blow moldable polycarbonate. The concentration of the branching agent in the blow-moldable polycarbonate is generally in the range of 0.2-0.8 mole percent, preferably 0.4-0.5 mole percent, based on the total moles of structural carbonate in the polycarbonate preform.

The second polycarbonate can be prepared by melt transesterification or interfacial methods. Both methods are well known in the art. The aforementioned second polycarbonate may comprise substantially unbranched polycarbonate. It may also comprise a branched polycarbonate incorporating a branching agent by any method including the method of the present invention and methods of the prior art such as the Krabbenhoft method.

The weight average molecular weight (Mw) of the polycarbonate preform and the second polycarbonate can be adjusted by changing the ratio of diaryl carbonate to dihydric phenol. When two different polycarbonate resins are mixed together and allowed to equilibrate, the molecular weight distribution of the equilibrium material generally approaches the weighted number average molecular weight of the two different resins. Accordingly, it is desirable to produce a preform having a molecular weight greater than or equal to the molecular weight of the second polycarbonate in which the preform will melt equilibrate. Thus, because of the incorporation of branching agents, blown polycarbonates exhibit little or no reduction in molecular weight.

The molecular weight (Mw) of the polycarbonate preform is preferably 10,000-60,000, more preferably 40,000-60,000.

The molecular weight (Mw) of the second polycarbonate is preferably 40,000-75,000.

The preferred range of molecular weight of blow moldable polycarbonate is 25000-55000, more preferred range is 40000-55000.

All the above molecular weight values are determined by gel permeation chromatography with reference to polystyrene.

Example 1

A polycarbonate preform was prepared containing 4 mole percent (based on the total moles of carbonate structural units in the polycarbonate preform) branching agent.

131.5g (0.576mol) 2,2-di(4-hydroxyphenyl) propane (BPA), 138.8g (0.648mol) diphenyl carbonate and 7.432g (0.024mol) 1,1,1-tri(hydroxyl Phenyl)ethane (THPE) was mixed in powder form in a 1 liter glass melt polymerization reactor. The glass reactor surfaces were previously passivated by pickling, rinsing and subsequent drying. The reaction vessel was deoxygenated by evacuating to about 1 Torr and then filling with purified nitrogen. The reaction vessel was immersed in a fluidized heat bath preheated to 180 °C. The reaction mixture was allowed to melt to give a homogeneous liquid. After becoming a complete solution, allow the system to thermally equilibrate for 5-10 minutes.

An aqueous solution of tetramethylammonium hydroxide (TMAH _aq ) (3×10 ^-4 mol) that can provide 5.0×10 ^-4 mol/mol BPA equivalent and 300 μl of 7.5×10 ^-6 mol/mol BPA equivalent A 0.025M aqueous sodium hydroxide solution was injected into the above solution. The resulting solution was stirred at 180°C for 5 minutes. At this point, the reaction temperature was raised to 210°C and the pressure dropped to 175 mmHg. Phenol started distilling out of the reactor immediately (approximately 3-4 drops/sec). After 35 minutes, the reactor pressure was reduced to 100 mmHg and held for an additional 35 minutes. During this period, phenol was continuously distilled into the receiving flask (1-2 drops/sec), the total volume received at the end of this 210°C period was 74ml. The reactor temperature was raised to 240°C (100 mmHg) and maintained at these conditions for 40 minutes. During this period, the average rate of phenol distillation was about 1 drop/3-5 seconds (a total of 93 ml was collected at this time). The reaction temperature was raised to 270°C (15 Torr) for 20 minutes. The reactor temperature was raised to 300°C (1.1 Torr) for 25 minutes in the final reactor stage. At this point, the solution started to foam (total distillate volume 105 ml). The solution was allowed to foam for 8 minutes, then the reaction was terminated. During the course of the reaction, a total of 115.5 g of distillate was collected.

The polycarbonate was dissolved in 1000 ml of dichloromethane and filtered through filter paper (no gelled or insoluble particles were received). The obtained homogeneous solution was placed in a mixer, and while stirring rapidly, an equivalent volume of methanol was added to cause precipitation. A white suspension was obtained which was filtered with suction. The resulting white powder was dried at 70° C. for 16 hours to obtain 96.3 g of a polycarbonate preform. It consists essentially of about 4 mole percent chemically bound [1,1,1-tris(hydroxyphenyl)ethane] carbonate units and about 96 mole percent chemically bound bisphenol A carbonate units. The molecular weight (Mw) of this polycarbonate preform was 50.798.

Example 2

Branching agents can be incorporated into the polycarbonate preform at concentrations as high as 10 mole percent.

According to the method of embodiment 1, make 123.2g (0.540mol) BPA, 138.8g (0.648mol) diphenyl carbonate and 18.54g (0.060mol) 1,1,1-three (hydroxyphenyl) ethane (THPE) reaction. The reaction mixture was allowed to melt to give a homogeneous liquid. After becoming a complete solution, allow the system to thermally equilibrate (5-10 minutes). The solution was stirred at a rate of 250 min/rev.

136 μl of 2.21 M tetramethylammonium formate (TMAF) solution was injected into the above solution as a basic catalyst. The resulting solution was stirred at 180°C for 5 minutes. At this point, the reaction temperature was raised to 210°C and the pressure dropped to 175 mmHg. Phenol started distilling out of the reactor immediately (approximately 3-4 drops/sec). After 35 minutes, the reactor pressure was reduced to 100 mmHg. Phenol was continuously distilled into the receiving flask (1-2 drops/sec; to a total of 80 ml). At this point, the reactor temperature was raised to 240°C (15 Torr) for 31 minutes. A total of 100 ml of distillate was collected at this time. The solution started to foam. Stop the reaction immediately. During the course of the reaction, a total of 112.6 g of distillate was collected.

According to the method of Example 1, 91.6 g of polycarbonate preforms were obtained. It consists essentially of about 10 mole percent chemically bound [1,1,1-tris(hydroxyphenyl)ethane] carbonate units and about 90 mole percent chemically bound bisphenol A carbonate units. The molecular weight (Mw) of this polycarbonate preform was 10140.

Embodiment 3 (comparative example)

It is difficult to incorporate branching agents into polycarbonate preforms at concentrations significantly higher than 10 mole percent.

According to the method of Example 1, make BPA, diphenyl carbonate and 1,1,1-tris (Hydroxyphenyl)ethane (THPE) mixture reaction. The material gelled during the reaction and was not further evaluated.

Example 4

The polycarbonate preform of Example 1 was melt equilibrated with Lexan ^(R) 130 grade polycarbonate (product of GEPlastics) to produce a blow moldable polycarbonate having 0.45 mole percent THPE branching agent. 250 ppm tetramethylammonium acetate was used per melt extrusion. Prior to extrusion, the materials were premixed in a Henschel mixer. Extrusion was carried out at a feed rate of 12 lb/hr, with a screw speed of 300-325 rpm and a vacuum exhaust to remove triethylamine catalyst by-products.

The resulting blow-moldable polycarbonates (c) were compared with essentially unbranched bisphenol A polycarbonates (a) and with branched bisphenol A polycarbonates (b) obtained by the Krabbenhoft process.

Preform Mol%THPE Mw OH(ppm) R ^* T(R ^* :ΩC)a. - None 51,827 250 1.6 265.3b. Pure 0.45 48,783 760 2.5 255.2c. 4.50% 0.45 50,900 570 2.8 261.2

The above results show that, compared to the molecular weight of the starting unbranched polycarbonate (a), the molecular weight of the blow-moldable polycarbonate (c) obtained by the process of the present invention is not as high as that obtained by the prior art process. The molecular weight of the branched polycarbonate (b) decreases that much.

In making polycarbonates it is desirable to keep the number of -OH groups to a minimum. Unbranched polycarbonate (a) has 250 ppm -OH. The number of -OH groups of the blow-moldable polycarbonate (c) according to the invention is almost one-third less than that of the prior art branched polycarbonate (b).

R ^* is a measure of the shear thinning behavior of a polymer. Experience has shown that good blow molding properties are obtained when R ^* is close to 3.0. The R ^* value can be obtained by measuring the complex viscosity with a rheodynamic spectrometer at three different temperatures (typically 230°C, 250°C and 270°C). Using this value into the Arrhenius equation, the optimum processing extrusion temperature can be calculated, which is the temperature at which the melt viscosity is 20,000 poise at 100 rad/s. The low shear viscosity at this temperature is then calculated. R ^* is calculated by dividing this viscosity by 20,000 poise.

The inventive blow moldable polycarbonate (c) exhibits an R ^* value of 2.8. It is closer to 3.0 than the prior art branched polycarbonate (b). Therefore, the blow moldable polycarbonates of the present invention are more suitable for blow molding.

T(R ^* ) indicates tack, which the blowable resin must remain tacky. The T(R ^* ) of the unbranched resin (a) is greater than 265°C. Using the prior art method, the T(R ^* ) of the branched polycarbonate (b) decreased by more than 10°C, indicating a decrease in the viscosity of the resin. However, using the method of the present invention, the T(R ^* ) of resin (c) was only reduced by 4°C, indicating a lesser reduction in tack.

Claims (19)

1. method for preparing blow moldable polycarbonates, it comprises the steps:

A. by being contacted, multifunctional branching agent, diaryl carbonate and dihydric phenol prepare branched polycarbonate preforms in fusion transesterification process; With

B. with the described polycarbonate preforms and the second polycarbonate melt balance.

2. according to the process of claim 1 wherein that described contact is under 170-380 ℃ the temperature, carry out in the presence of the polymerization catalyst of effective dose.

3. according to the method for claim 2, wherein said polymerization catalyst is selected from acetate tetramethyl-ammonium, formic acid tetramethyl-ammonium, hydroxide aryl ammonium and hydroxide Fang Ji Phosphonium, carboxylate, phenates and borate.

4. according to the process of claim 1 wherein that described diaryl carbonate comprises diphenyl carbonate.

5. according to the process of claim 1 wherein that described dihydric phenol comprises 2,2-two (4-hydroxy phenyl) propane.

6. according to the process of claim 1 wherein that described multifunctional branching agent is selected from trihydroxy phenol and tetrahydroxy phenol.

7. according to the process of claim 1 wherein that described multifunctional branching agent comprises 1,1,1-three (4-hydroxy phenyl) ethane.

8. according to the process of claim 1 wherein, based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, the addition of described multifunctional branching agent is 2.1-10% (mole).

9. according to the process of claim 1 wherein, based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, the addition of described multifunctional branching agent is 4-6% (mole).

10. according to the method for claim 1, wherein said polycarbonate preforms is with the second polycarbonate melt balance, based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, the amount of polycarbonate preforms should make that branching agent concentration is 0.2-0.8% (mole) in blow moldable polycarbonates.

11. method according to claim 1, wherein with the described polycarbonate preforms and the second polycarbonate melt balance, based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, the amount of polycarbonate preforms should make that branching agent concentration is 0.4-0.5% (mole) in blow moldable polycarbonates.

12. according to the process of claim 1 wherein that described second Merlon prepares with the fusion transesterification process.

13. according to the process of claim 1 wherein that described second Merlon prepares with the interface method.

14. form according to the process of claim 1 wherein that described second Merlon is gone up substantially by nonbranched Merlon.

15. according to the process of claim 1 wherein that described second Merlon comprises branched polycarbonate.

16. Zhi Bei blow moldable polycarbonates in accordance with the method for claim 1.

17. method for preparing polycarbonate preforms, it comprises contacts multifunctional branching agent, diaryl carbonate and dihydric phenol in fusion transesterification process, the concentration of multifunctional branching agent wherein, based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, be 2.1-10% (mole).

18. according to the method for claim 17, wherein the concentration of multifunctional branching agent based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, is 4-6% (mole).

19. a polycarbonate preforms, based on the total mole number meter of structure carbonate unit in the polycarbonate preforms, it comprises the multifunctional branching agent of 2.1-10% (mole).